Boyce said the air operation was "impressive" so far but added: "We are very much still at the beginning. We are there for the long haul."

And, asked what the timescale of the campaign was, he said: "We must expect
to go through the winter and into next summer at the very least."

Hoon said he was aware of Taliban claims that more than 100 civilians had been killed in the latest strikes. He said those claims could not be independently confirmed but asserted all efforts were being made to avoid civilian deaths.

"There is always going to be a risk, that can not be avoided," he said.

"It is becoming clear that the U.S. and UK carefully targeted strikes are increasingly effective," Hoon said. "We have inflicted damage on bin Laden's organisation, terrorist training camps and the military infrastructure of the Taliban regime that shelters and protects him."

The defence minister said: "It is clear that the coalition is already having an impact on Taliban cohesion. Reports suggest that some of (Taliban supreme leader) Mullah Omar's followers are starting to have second thoughts. Some are clearly defecting."

However, he said the defections were not at a level that would suggest the Taliban are losing control of the government.

Boyce said the coalition had air superiority over Afghanistan, but U.S. and British planes still face threats from portable anti-aircraft missiles and anti-aircraft guns.

He said British reconnaissance and aerial refuelling planes were supporting the strikes by U.S. combat aircraft.

Boyce said Britain's forces had not launched any combat strikes since its submarines fired cruise missiles at Afghanistan last Sunday and added that there may be a lull in the bombing as the impact of the attacks is assessed.